The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Erection problems signal heart disease

MELBOURNE, Jan 30 AAP - Men suffering erection difficulties should be screened for heart disease, say researchers who found the problem pointed to an increased risk of cardiovascular issues.

The world's largest study to examine links between erectile dysfunction and heart disease, undertaken in Australia, found even minor erection difficulties could indicate heart problems and an increased risk of dying early from any cause.

The study, involving 95,000 Australian men, linked the problem to an increased risk of a range of cardiovascular events including heart attack, heart failure and circulation problems.

Lead researcher Professor Emily Banks said the results showed men with severe erectile dysfunction had a 60 per cent increased risk of coronary artery disease, compared to men with no erectile dysfunction.

Those with severe erection problems also had almost double the risk of dying than those without, Prof Banks said.

For men who already had heart disease, erectile dysfunction could predict a subsequent cardiac event, she said.

Erection problems could predict the risk of heart problems over and above other factors including smoking, diabetes and overweight, Prof Banks said.

"We found that the ability to predict risk was very similar in men with and without a past history of cardiovascular disease," Prof Banks told AAP.

"If you have erectile dysfunction you really need to take action and go to your doctor and ask for a heart check, if you haven't been assessed before," she said.

The study, published in the journal PLOS Medicine, emphasised erection problems were not the cause of heart disease but were an indicator men were at increased risk.

This was likely because the condition indicated a problem with blocked blood vessels or poor blood flow, which is also associated with cardiovascular disease.

Heart Foundation cardiovascular health director Dr Rob Grenfell said: "If you have erection issues, it's a warning that you may also have issues with your heart."

The research analysed data from the Sax Institute's 45 and Up study, an ongoing study of healthy ageing, and involved the Heart Foundation and the NSW government.